The present disclosure relates to set devices having a function for controlling removable cards such as SD cards and embedded modules corresponding to the removable cards.
Multimedia start to be in widespread use in portable devices. Slots of small card media such as SD cards are mounted to cellular phone terminals, and these cellular phone terminals are used a lot as external storage media. Conventionally, in order to control small card media, a card host LSI has been connected to the outside of a microcomputer LSI in a portable telephone terminal, and the card host LSI has accessed to the small card media.
In general, low-speed general-purpose port terminals for mainly performing serial communication and terminal control, and high-speed IO bus terminals for mainly performing parallel communication are present as external communication terminals of the microcomputer LSI. The connection between the microcomputer LSI and the card host LSI is controlled by using not general-purpose ports but higher-speed IO buses in order to realize high-speed communication of data.
FIG. 14 is a diagram illustrating one example of a conventional constitution of a set device using the card host LSI. The set device 500 shown in FIG. 14 has a main microcomputer LSI 50, a card host LSI 501, and peripheral IO-LSIs 27a and 27b. A SD card 110 is attachable to the set device 500.
The peripheral IO-LSIs 27a and 27b, and the card host LSI 501 are connected to the main microcomputer LSI 50 via an IO bus IB2. An IO bus I/F 51 in the main microcomputer LSI 50 functions as a master of the IO bus IB2, and the peripheral IO-LSIs 27a and 27b, and the card host LSI 501 are slave devices of the IO bus IB2.
The card host LSI 501 has an SD card host I/F 531 that is controlled by register setting from the IO bus IB2, and functions as a master of a card bus CB2 for SD cards. The SD card host I/F 531 reads and writes data in an SD card 110 via the card bus CB2 according to the control from the IO bus IB2.
FIG. 15 is a diagram illustrating a detailed constitution of the IO bus IB2. The IO bus IB2 is composed of a 7-bit address line, a 16-bit bidirectional data line, a write enable line, a read enable line, and one-bit chip selects 1, 2 and 3.
An IO bus I/F 51 in the main microcomputer LSI 50 outputs an address signal, a write enable signal and a read enable signal to the card host LSI 501 and the peripheral IO-LSIs 27a and 27b as the slave devices. Further, the IO bus I/F 51 performs bidirectional data communication with slave device selected by the chip selects 1, 2 and 3. The card host LSI 501 and the peripheral IO-LSIs 27a and 27b output interrupt signals to the main microcomputer LSI 50.
FIG. 16 is a diagram illustrating a detailed constitution of the card bus CB2. The card bus CB2 is composed of a one-bit bidirectional command line, a four-bit bidirectional data line, and one-bit clock line. The SD card host I/F 531 in the card host LSI 501 outputs a clock to the SD card 110. The SD card host I/F 531 transmits and receives a command and data in synchronization with the clock.
With the above constitution, the set device 500 is compatible with small card media such as SD cards.